1. Field of the Invention
The present invention relates to a valve operating system in an internal combustion engine, comprising a cylindrical swinging support section provided at a base end of a rocker arm and swingably carried on a rocker shaft mounted in a cylinder head, a plurality of boss portions formed at a tip end of the rocker arm and arranged in a direction parallel to an axis of the rocker shaft, tappet screws being threadedly fitted into the boss portions and capable of being individually put into abutment against upper ends of a plurality of engine valves, and cam abutments provided on the rocker arm in an intermediate portion thereof between the swinging support section and the boss portions to come into contact with a valve operating cam.
2. Description of the Related Art
Such a valve operating system is conventionally known, for example, from Japanese Patent Application Laid-open No. 6-185322.
In the above known system, however, the plurality of boss portions with the tappet screws threadedly fitted therein are formed at tip ends of a plurality of arms disposed at locations spaced from one another in a direction along the axis of the rocker shaft, and a relatively large load is applied to each of the boss portions during a valve driving operation. Nevertheless, it is not easy to say that the rigidity of each of the boss portions, i.e., the rigidity of the tip end of the rocker arm is sufficient.
Accordingly, it is an object of the present invention to provide a valve operating system in an internal combustion engine, wherein a rigidity of a rocker arm having a plurality of boss portions with a tappet screws threadedly fitted therein can be enhanced sufficiently.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a valve operating system in an internal combustion engine, comprising a cylindrical swinging support section provided at a base end of a rocker arm and swingably carried on a rocker shaft mounted in a cylinder head, a plurality of boss portions formed at a tip end of the rocker arm and arranged in a direction parallel to an axis of the rocker shaft, tappet screws being threadedly fitted into the boss portions and capable of being individually put into abutment against upper ends of a plurality of engine valves, and cam abutments provided on the rocker arm in an intermediate portion between the swinging support section and the boss portions to come into contact with a valve operating cam, wherein the boss portions are interconnected by a connection wall having a plurality of wall portions which intersect each other at right angles in a plane perpendicular to the axis of the rocker shaft.
With such arrangement of the first feature, the boss portions are interconnected by the connection wall and hence, the rigidity of the tip end of the rocker arm for driving the plurality of engine valves can be enhanced sufficiently. Moreover, the connection wall has the plurality of wall portions which intersect one another at the right angles in the plane perpendicular to the axis of the rocker shaft, i.e., an axis of swinging movement of the rocker arm. Therefore, it is possible to suppress an increase in weight of the rocker arm due to the connection wall to the minimum, while maintaining a sufficient connecting rigidity.
According to a second aspect and feature of the present invention, in addition to the first feature, the connection wall is formed into a substantially U-shape in cross-section. With such arrangement of the second feature, it is possible to suppress an increase in weight due to the connection wall.
According to a third aspect and feature of the present invention, in addition to the first or second feature, the connection wall is provided with a plurality of ribs which intersect each other and which are connected to the wall portions, respectively. With such arrangement of the third feature, it is possible to further enhance the rigidity of the tip end of the rocker arm.
According to a fourth aspect and feature of the present invention, in addition to the first feature, the boss portions are interconnected by the connection wall having the wall portion, an outer surface of which is connected flush to outer peripheral surfaces of the tip ends of the boss portions.
With such arrangement of the fourth feature, the boss portions can be formed so that they do not protrude, thereby eliminating the concentration of a stress on a connection between the connection wall and each of the boss portions, and it is possible to enhance the durability of the rocker arm, while sufficiently enhancing the rigidity of the tip end of the rocker arm.
According to a fifth aspect and feature of the present invention, in addition to the first feature, the rocker arm is provided with an opening, a portion of a side of which is formed by an inner surface of the connection wall, and a roller which is the cam abutment is accommodated in the opening and rotatably carried on a roller shaft fixed to the rocker arm. With such arrangement of the fifth feature, the connection wall can be disposed in proximity to the roller, whereby the rigidity of supporting of the roller can be enhanced.
According to a sixth aspect and feature of the present invention, in addition to the first feature, the rocker arm is provided with first and second support walls, at tip ends of which the tappet screws at axially one end and the axially other end of the rocker shaft are mounted, and the connection wall which interconnects tip ends of the first and second support walls, and the rocker arm has recesses defined at least in an upper surface thereof in an area surrounded by the first and second support walls, the connection wall and the swinging support portion.
With such arrangement of the sixth feature, the entire outer periphery of the rocker arm is formed by the swinging support section, the pair of support walls and the connection wall, and the recesses are defined at least in the upper surface of the rocker arm. Therefore, it is possible to reduce the weight of the rocker arm, while avoiding a reduction in rigidity of the rocker arm.
According to a seventh aspect and feature of the present invention, in addition to the sixth feature, the rocker arm is provided with an opening in which a roller which is the cam abutment is accommodated; a roller shaft rotatably supporting the roller is fixed across the opening; and the recesses are defined in the upper surface of the rocker arm so that oil can be supplied to the roller within the opening.
With such arrangement of the seventh feature, the oil accumulated in the recesses can be supplied to the roller to lubricate the roller and hence, it is unnecessary to provide a passage for supplying the oil to the roller in the rocker arm, leading to a reduced number of steps of processing the rocker arm.
According to an eighth aspect and feature of the present invention, in addition to the seventh feature, the rocker arm has a pair of shaft support portions provided thereon between the opening and the first and second support walls for supporting opposite ends of the roller shaft, and the recess is defined in the rocker arm between the shaft support portions and the swinging support section. With such arrangement of the eighth feature, the oil can be accumulated reliably in a portion of the rocker arm which is swung in a relatively small amount, thereby reliably lubricating the roller.
According to a ninth aspect and feature of the present invention, in addition to the seventh feature, the rocker arm has a pair of shaft support portions provided thereon between the opening and the first and second support walls for supporting opposite ends of the roller shaft, and the recess is defined in the rocker arm between the shaft support portions and the connection wall. With such arrangement of the ninth feature, it is possible to reduce the weight of the tip end side of the rocker arm to alleviate the inertial weight, while performing the lubrication of the roller.
According to a tenth aspect and feature of the present invention, there is provided a valve operating system in an internal combustion engine, comprising a cylindrical swinging support section provided at a base end of a rocker arm and swingably carried on a rocker shaft mounted in a cylinder head, a plurality of boss portions formed at a tip end of the rocker arm and arranged in a direction parallel to an axis of the rocker shaft, tappet screws being threadedly fitted into the boss portions and capable of being individually put into abutment against upper ends of a plurality of engine valves, and cam abutments provided on the rocker arm in an intermediate portion thereof between the swinging support section and the boss portions to come into contact with a valve operating cam, wherein the boss portions are interconnected by a connection wall having a wall portion, an outer surface of which is connected flush to outer peripheral surfaces of tip ends of the boss portions.
With such arrangement of the tenth feature, the boss portions can be formed so as not to protrude, thereby eliminating the concentration of a stress on the connection between the connection wall and each of the boss portions, and it is possible to enhance the durability of the rocker arm, while sufficiently enhancing the rigidity of the tip end of the rocker arm.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.